1. Field of the Invention
The present invention relates to a cement soil apparatus of underground borer and a method of forming an underground hole.
2. Description of the Prior Art
Generally, in civil engineering foundation works, construction of board piles (field-made piles) or insertion of P.C piles, H beam piles, steel piles or the like in various kinds of grounds is carried out with the aim of increasing the foundation ground bearing capacity.
In carrying out foundation works as above, when a stratum in which much water springs up, a boulder formation, a conglomerate formation and the like are bored with the conventional working method, a bored hole will collapse in many cases, raising a problem that the aforementioned pile or the like cannot be inserted to a bored depth. Even if a pile can be inserted to a depth of a bored hole, there arises another problem that in some cases, the pile will settle owing to insufficient ground bearing power.
In order to solve the above problems, during execution of field work, operation has hitherto been carried out in which a cylindrical iron pipe is inserted to a bored depth after boring by such a method as pile driving, clay in the cylindrical iron pipe is removed and cement paste is then grouted into the inside of the cylindrical iron pipe, and the cylindrical iron pipe is pulled up by means of a separate crane during curing of cement. Such operation, however, requires a complicated operation process including boring, insertion of the cylindrical iron pipe, cleaning of the inside of the cylindrical iron pipe, grouting of cement and pull-up of the cylindrical iron pipe, thus needing many different apparatus therefor, and because of complexiety of exchange of various apparatus, a great operation cost is needed.